Randau Best on sun 25 aug 96
My friend makes mirror frames 15 * 12 inch between 7/16 and 5/8 inch thick.
She uses Highwater Phoenix Clay which she bisques ^05, fires ox ^6,
luster fires ^019 with a 15 minute hold.
The problem she faces is that the frames break cleanly at opposite
corners, only in the luster firing. She checked for cracks before the
luster firing, finding none.
Does anyone have any thoughts to help us solve this problem?
Sarah in NC
Ron Roy on mon 26 aug 96
Sounds like this is dunting - cracking at either the cristobalite or the
quartz inversion. Slow the firing down.
Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849
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